Studies will be continued of a growth hormone (GH) precursor, pregrowth hormone. These experiments will involve translation of RNA or polysomes from a line of rat pituitary tumor cells (GC or GH3) in cell-free systems, and incubations of intact pituitary tumor cells and normal rat pituitaries. Investigations will be continued of the stimulation by the synthetic glucocorticoid dexamethasone of GH synthesis by GH3 cells. Studies will be performed of the effects of dexamethasone of intracellular levels of GH messenger RNA (mRNA), and ultimately on GH mRNA transcription. The characterization and isolation of GH mRNA will be continued. Complementary DNA copies of purified GH mRNA will be synthesized and employed in the studies of the regulation by dexamethasone of GH mRNA in the GH3 cells.